I wanted to take a look at this, so I ran this on 2.7.2, It ws consistently 100 bytes off, so I put -50 for the seek_back. The file.tell() returned a position higher than the beginning current position, still 100 bytes off.
==============
Current fd position: 4202
seeking back: 50
fd position after seek: 4252
Traceback (most recent call last):
File "/home/patrick/jython/dist/Lib/test/bugs/issue_2363.py", line 13, in <module>
assert file.tell()==4152
AssertionError
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Does this mean that file.tell() doesn't give the absolute position, or it doesn't indicate the last position in the file?
Populating the test.log file with different characters produce differrent results, obviously.